1. Field of the Invention
This invention relates to silylated vinyl alcohol polymers, that is, polymers of ethenyloxysilanes, and to their preparation.
2. Background
Ethenyloxysilanes are known compounds or are prepared by known methods, for example, as described by Jung et al., Tetrahedron Lett., 3791 (1977); polymers prepared therefrom are also known. For example, U.S. Pat. No. 3,418,293 discloses the polymerization of vinyloxysilanes of the formula CH.sub.2 .dbd.CHOSi(R.sup.1)(R.sup.2)(R.sup.3) wherein R.sup.1, R.sup.2 and R.sup.3 are the same or different, and each is a hydrocarbon radical which can include alkyl, cycloalkyl, aryl, aralkyl and alkaryl, in the presence of an ionic catalyst of the Friedel-Crafts or Ziegler type , at a temperature in the range -80.degree. C. to 0.degree. C., in an anhydrous organic solvent. The polymerization product is a poly[(ethenyloxy)triorganosilane] which can be converted to poly(vinyl alcohol) by alcoholysis. Other processes for polymerizing silanes, employing free radicals or compounds such as SnCl.sub.4 or ethyl aluminum chlorides, but not aldehydes, as initiators, are disclosed in the art, for example, as follows.
Murahashi et al., Polymer Letters 3, 245 (1965) and 4, 59, 65 and 187 (1966), disclose the preparation of poly(vinyltrimethylsilyl ethers) by radical and cation-initiated polymerization of vinyloxy trimethylsilane and conversion thereof to stereoregular poly(vinyl alcohol). Also disclosed is the radical-initiated copolymerization of vinyloxy trimethylsilane ([ethenyloxy]trimethylsilane) with vinyl comonomers. Cationic initiators employed were SnCl.sub.4 or ethyl aluminum chlorides. Nozakura et al., J. Polymer Sci., Polymer Chem. Ed., 11, 1053 (1973), disclose the polymerization of several ethenyloxy trialkylsilanes initiated by cationic compounds SnCl.sub.4 or ethyl aluminum chlorides, and conversion of the poly(vinyltrialkylsilyl ethers) to poly(vinyl alcohol) with aqueous hydrofluoric acid. Runge et al., Makromol. Chem., 120, 148 (1968), disclose the free radical-initiated copolymerization of ethenyloxytrimethylsilane with vinyl comonomers. Japanese published, unexamined application JA 22299/69 discloses a process of copolymerizing ethenyloxytrialkylsilanes with vinyl comonomers in the presence of radical catalysts such as azo-bis(isobutyronitrile). Colvin, "Silicon in Organic Synthesis". Butterworths, 1981, pages 219-220, discloses the reaction of alicyclic silyl enol ethers with aldehydes in the presence of a fluoride ion catalyst, for example, ##STR1## Colvin, ibid, page 227, discloses the reaction of aromatic aldehydes with silyl ketene acetals in the presence of TiCl.sub.4 ; the silyl group in the product is subsequently removed by hydrolysis, for example, ##STR2## Colvin, ibid, pages 221 and 222, discloses the reaction of certain alkyl and aralkyl halides with silyl enol ethers in the presence of TiCl.sub.4 or ZnBr.sub.2, for example, ##STR3## Colvin, ibid, pages 232-236, discloses the reaction of silyl enol ethers with acyl halides, halogenated acid anhydrides and ketones in the presence of Lewis acids.
The conversion of pendant siloxy groups, such as --OSi(CH.sub.3).sub.3, to hydroxyl groups in polymers by a variety of methods is disclosed in the aforesaid publications of Murahashi and Colvin and in the Japanese publication.
U.S. Pat. No. 2,165,962 and Hoaglin et al., J. Am. Chem. Soc., 71, 3468 (1949) describe the polymerization of alkyl vinyl ethers in the presence of acetals such as acetaldehyde acetal and a Lewis acid such as BF.sub.3 to form acetal-capped polyvinyl ethers; for example, ##STR4## Acetal-initiated polymerization of trialkylsilylvinyl ethers is not disclosed. Formation of unsaturated aldehydes by hydrolysis of a 1,1,3-trialkoxy product formed by the condensation of an acetal with a vinyl ether is disclosed by Fishman et al., Synthesis Comm., 137 (1981); for example, ##STR5##